Earth's iron core may have been squeezed through rocks

A team of Earth scientists at Stanford University have shown that iron can flow out of rock at high
pressures, yielding new theories on how the core of our planet
formed.

The team, led by Wendy Mao, squeezed rocks containing iron to
huge pressures between the tips of a pair of diamonds, and imaged
the result with X-rays. They saw molten metal flowing through the
rocks.

The exact process under which the Earth's core formed has been
under debate for some time. The most commonly accepted theory is
that the iron that comprises the planet's core separated early in
the planet's life when the area outside the core was still liquid,
sinking with gravity to the centre in a way similar to how wax moves within a
lava lamp.

However, Mao's results suggest a different process - that the
iron was able to travel through the solid mantle later in the
Earth's lifespan, percolating through to the centre. Their results
were published in Nature Geoscience.

"In order for percolation to be efficient, the molten iron needs
to be able to form continuous channels through the solid," Mao told
the BBC. "Scientists had said this theory wasn't
possible, but now we're saying -- under certain conditions that we
know exist in the planet -- it could happen. So, this brings back
another possibility for how the core might have formed."

That possibility means that the formation of the core may not
have happened all at once, as previously assumed, but in a series
of stages that then had an influence on the chemistry of our
planet's interior.

More work will be necessary to know for sure, but Mao says this
knowledge is within our grasp: "We know that Earth today has a core
and a mantle that are differentiated. With improving technology, we
can look at different mechanisms of how this came to be in a new
light."